The goal of this project is to understand the bioacoustic and neurobehavioral basis of acoustic communication in insects, and the mechanisms underlying sound localization. Insects have proved to be good model systems for studying auditory neurobiology and behavior. We will investigate the tympanal hearing organs of an acoustic parasitoid fly, Ormia ochracea, because this insect appears to have "invented," in the evolutionary sense, a novel way to detect the direction of a sound source. Laser vibrometry is used to study the fly~s tympanal mechanics. The fly's eardrums are a new type of directional receiver: their mechanical response to sound permits them to overcome the extremely small ineraural difference cues that result from their minuscule size compared to much longer wavelength of the 5 kHz stimulus, that the fly must detect and localize. Even so, because of the fly~s small size, the magnitude of interaural disparity cues that are processed by the CNS for sound localization is still limited. Therefore this research will be directed at uncovering the auditory processing that underlies time coding in the fly~s nervous system. The findings from this investigation could have potential health relatedness if a miniature microphone based on the Ormiine fly's ears could be produced. Such a device might be small enough to confer directionality to hearing aids. The well-known and widely investigated acoustic startle response (ASR) of mammals as many parallels with the ultrasound ASR of flying crickets. Behavioral and psychoacoustic studies have been performed that show that the ASR of crickets can serve as a model system to investigate mechanisms of auditory processing that are ordinarily studied in vertebrates, including mammals. These include the precedence effect, habituation, dishabituation, sensitization, and categorical perception. In the cricket, however, the neural basis underlying auditory processing is subserved by much simpler neural systems, and it is here presented as a model system in which to investigate the neural processing that underlies complex acoustic behavior.